1. Field of the Invention
This invention relates to a method for preparing 3,3-dimethylbutyraldehyde from a tert-butyl cation precursor, vinyl halides or acetylene, and an inorganic acid.
2. Related Background Art
Reactions of carbocation precursors, e.g., alkenes or alcohols, with alkenes, haloalkenes, or acetylene in the presence of an inorganic acid are well known, as reviewed by K. Bott, Angew. Chem., International Ed. (English), Vol. 19, pgs. 171-178.
The reaction of isobutylene with ethylene and sulfuric acid, followed by hydrolysis is known to produce 3,3-dimethylbutanol, as disclosed in British Patent No. 693,390.
Japanese Patent JP 02-006429 discloses the reaction of isobutylene with vinylidene dichloride and sulfuric acid, followed by hydrolysis to produce 3,3-dimethylbutyric acid.
Reactions of 1-adamantanol and its bridgehead derivatives with acetylene in sulfuric acid to generate aldehydes are disclosed by L. Bott in Tetrahedron Lett. (1969), pg. 1747, and Justus Liebigs Ann. Chem. Vol. 766 (1972), pg. 766.
Reaction of N-(hydroxymethyl)phthalimide with vinyl chloride in the presence of concentrated sulfuric acid to generate an aldehyde is disclosed in K. Bott, Tetrahedron Letters, (1970), pages 4301-04; K. Bott, Chemische Berichte, Vol. 106, pages 2513-22 (1973); and K. Bott, Angewandte Chemie International Edition (English), Vol. 19, pages 171-178 (1980). However, no suggestion is made that 3,3-dimethylbutyraldehyde could be synthesized in this manner.
There is no suggestion to react a tert-butyl cation precursor, vinyl halides, or acetylene, and an inorganic acid followed by hydrolysis to produce 3,3-dimethylbutyraldehyde.
3,3-Dimethylbutyraldehyde is an intermediate that is useful in the preparation of the sweetener N-[N-(3,3-dimethylbutyl)-L-.alpha.-aspartyl]-L-phenylalanine disclosed in U.S. Pat. No. 5,480,668 and U.S. Pat. No. 5,510,508. Accordingly, a method for preparing that intermediate which is both economical and specific is highly desired.